Bug 2355513 (CVE-2022-49755)

Summary:	CVE-2022-49755 kernel: usb: gadget: f_fs: Prevent race during ffs_ep0_queue_wait
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	dfreiber, drow, jburrell, vkumar
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2025-03-27 17:05:01 UTC

In the Linux kernel, the following vulnerability has been resolved:

usb: gadget: f_fs: Prevent race during ffs_ep0_queue_wait

While performing fast composition switch, there is a possibility that the
process of ffs_ep0_write/ffs_ep0_read get into a race condition
due to ep0req being freed up from functionfs_unbind.

Consider the scenario that the ffs_ep0_write calls the ffs_ep0_queue_wait
by taking a lock &ffs->ev.waitq.lock. However, the functionfs_unbind isn't
bounded so it can go ahead and mark the ep0req to NULL, and since there
is no NULL check in ffs_ep0_queue_wait we will end up in use-after-free.

Fix this by making a serialized execution between the two functions using
a mutex_lock(ffs->mutex).

Comment 1 Robb Gatica 2025-03-27 20:21:40 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025032701-CVE-2022-49755-dfb6@gregkh/T

Comment 2 Avinash Hanwate 2025-03-28 04:37:41 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025032701-CVE-2022-49755-dfb6@gregkh/T